This Lightroom update caught me by surprise. A word of caution for subscribers of the CC version, though: I’ve seen several reports of problems when upgrading via Adobe’s Creative Cloud application. For what it’s worth, I upgraded it on my main machine without any issues whatsoever.
Being a CC subscriber myself, I didn’t give it much thought before upgrading, but owners of the standalone version of Lightroom 5 will have to check out the changes to decide whether the upgrade is worth it for them. I haven’t had much time to play with it yet, but this review by The Phoblographer covers all new features and changes in the new version. They liked it enough to give it an Editor’s Choice award, so it seems like a solid update.